Coal and other fossil fuels are strategic fuels around the world and make up one of the most abundant energy resources available. The development of low CO2 emissions is critical to delivery of clean energy and climate control associated with fossil fuel use. Carbon dioxide capture-enabling technologies in coal-fired energy arena include integrated coal gasification technology. This technology uses sequestration technologies, but does not involve the chemical conversion of CO2 to oxygen or other useful products.
Coal gasification processes provide for the conversion of coal, char, or coke to a gaseous product by reaction with heated air, oxygen, steam, or carbon dioxide or mixtures. The product of coal gasification is a mixture containing hydrogen and carbon monoxide and varying amounts of nitrogen, carbon dioxide, steam, hydrogen sulfide, organic sulfur compounds, tar, and small amounts of other contaminants depending on the selected gasification process.
Coal gasification involves a method of producing a syngas from coal and oxygen at a constant rate under defined pressure and temperature regions. Later the process requires removing sulfur compounds and other contaminants, followed by feeding the cleaned syngas to a chemical (for example methanol) synthesis reaction. The unconverted syngas can be burned for direct base load power generation replacing more expensive fuels. The gasification process produces a synthesis gas having, typically, a 1.2/1 ratio of CO to H2 and a lesser amount of CO2, S, CH4, among others. The stoichiometric requirement will limit the conversion of the syngas stream. Since only a limited fraction, typically about 50% of the available hydrogen is converted in the once-through methanol synthesis, the process will convert a maximum of only about 25% of the available syngas to a storable liquid methanol fuel. In the conventional production of methanol, the CO component of the syngas is partially shifted by reaction with water vapor in a water gas reaction to produce CO2 and additional H2.